Making Predictions

The expression “Go big or go home” means to do something to the fullest—but it doesn’t translate well into the materials science field, where “Go small or go home” is perhaps now more apropos.

As engineering moves further into nanoscale technologies, computational materials scientists like Professor Tianshu Li of the Department of Civil and Environmental Engineering are playing an increasingly important role in the materials science field, a field once dominated by experimentalists.

Li currently is working on simulating the formation of both ice and methane hydrates and on exploring an emerging nano material called mono-layer MoS2 (molybdenum disulfide). These materials may hold great promise in the energy, environmental, and electronics fields, but their properties must first be understood.

The properties of material behavior—for example, how a given material elastically responds to an external stress—are generally dominated by the interactions among atoms. “Once we can describe this information accurately,” explains Li, “we are, in principle, able to predict any kind of behavior in materials in the macroscopic world. This is the basic idea of computational materials science.”

At the nanoscale, experimentalists do not have enough resolution to be able to see a material’s behavior. Using computer modeling, however, Li can selectively turn on or off specific physical processes to verify their relevance. He can then share this knowledge with the experimentalists to tell them which material system to study to look for the desired material behavior. This approach saves time and money in the experimental phase.

Ice formation is one of those important processes that science would like to understand better. In the upper troposphere, ice particles grow from embryos that are only a few nanometers in size and form in a few nanoseconds. So no direct way exists to observe the embryos’ formation. These ice particles form clouds in very high altitudes that absorb solar radiation and protect the earth. If the particles’ formation could be better understood, perhaps through computer modeling and simulation, scientists may be better able to predict the global radiation budget and future climate change.

Methane hydrates are another important material, and Li has received an American Chemical Society Petroleum Research Fund Doctoral Investigator Award to study their formation. The methane hydrate compound occurs abundantly in nature and stores approximately twice the amount of energy found in all fossil fuels combined. Given the world’s growing energy needs, great interest exists in better understanding and tapping this potentially enormous resource.